Over the past few weeks, we have been driving a cross-ecosystem effort to replace the “monkey-patching” that powers all JavaScript APM tools today with something built into the runtime. Here is why, how, and where it stands.
This applies to server-side JavaScript only (Node.js, Bun, Deno, Cloudflare Workers). Browsers do not have diagnostics_channel and lack the async context propagation primitives needed to polyfill it.
Monkey-patching does not scale
My teammate Sigrid wrote a detailed breakdown of why monkey-patching is failing and how TracingChannel solves it.
The short version: every JavaScript APM tool, including Sentry’s, instruments libraries by intercepting require() and import calls at runtime using import-in-the-middle (IITM) and require-in-the-middle (RITM). This breaks with ECMAScript Modules (ESM), does not work in non-Node runtimes, conflicts with bundlers, and couples us to internal implementation details we do not control. The SDK also must load before the library it instruments, or instrumentation silently does nothing.
